Aeroplane-propeller



R. M. SHAFFER.

AEROPLANE PROPELLER.

APPLICATION FILED SEPT. 20, 1917.

Patented May 4, 1920.

,UNrTnp sTaTEs rATaNT onirica.

RICHARD M.. SHAFFER, 0F BALTIMORE, MAEYLANI), .ASSIGNOR 0F ONE-FOURTH TO CHARLES 2B. MANN ANI) ONE-FOURTH if@ @T-TELES B. MANN, JR., BOTH OF :BA1/TIPv MORE, MARYLAND.

T0 all whom t may concern:

Be it known that I, RICHARD M. SHAFFER, a citizen of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improve ments in Aeroplanedropellers, of which the following is a specification. l

This invention relates to improvements in propellers for air-craft. n

One object of the invention is to provide an improved construction of propeller in which the blades thereof are effectively braced against strains that tend to bend the same in a direction at right angles to their flat faces and which yare further braced against edgewise rearward strains or strains in a direction reversel to that in which the blades are revolving.

A further object of the invention is to provide an improved construction of aircraft propeller employing a plurality of main blades and a bracing blade for each main blade,-the entering and trailing edges of the bracing blades being out of alinement with the entering and trailing edges of the main blades.

still further object of the inventionis to provide an improved construction of airv craft propeller employing main and bracing blades so arranged that the bracing blade has a position to lap the trailing edge' of the main blade, and i A further obl'ect is to provide in an aircraft propeller a blade structure embodying a main and a bracing blade,the bracing blade having its outer end connected to the outer end of the mainblade and from said outer end the bracing blade extending away from the main blade and being non-parallel therewith.

With the above, and other objects in view, the invention is illustrated in the accom# panying drawing which latter, however, is in no way intended to define or limit the scope of the invention, but has for its function, merely, to illustrate a form of structure embodying the inventive idea.

In the drawing,-

Figure l, shows the propeller in rear elevation or as viewed from the rear side with respect to the direction in which it advances.

Fig. 2, illustrates the same in front eleva tion.

Specification of Letters Eatent.

Patented May 4C, 1920.

Application mea september ao, 1917. serial No. 192,278.

Fig. 3, shows the same in edge view.

Referring to the drawing the numeral 5, designates a hub structure, in the present instance of tubular form but which may be of any desired form so far as the present invention is concerned. In this instance the hub is provided with two radially-extending flat plates 6, one diametrically opposite the other, and at slight incline with respect to the aXis of the hub, for a purpose that will presently be explained.

In the present` illustration the two main blades 7 and 8, are shown as separate pieces of wood; the shape or outline'of these wood blades may diifer from that shown. As here shown the blades have narrow portions 9, near the hub which portions are lapped over or seated upon the iiat metal plates 6, to which they are rigidly secured by screws or fastenings l0. It is common for two blades projecting oppositely from a hub to have one piece of wood extending from tip to tip and to be built up of plies or laminati ons,.which are thickest at the hub and said one piece to extend from the tip end of one blade to the tip end of the other blade,-a hub structure being` fitted to such propeller intermediate the two blades and the ends being thinnest. Blades of this structure may be utilized in connection with the bracing feature of my invention.

In carrying out my invention I provide a hub having radially-extending supporting devices ll, which devicesv are spaced from and located at one side of the attaching means 6, for the main blades, as clearly shown in Fig. 3, ofthe drawing. In the present instance these supporting devices l1, have the form of fiat lugs or plates, which are located slightly to the rear of the plates 6. to whichv the main blades are attached, as readily seen in Figs. 2 and 3, of the drawing, so that during the revolution ofthe propeller the supporting lugs or plates 11, will travel in a circular path just behind the radial flat plates 6. It is to be understood that the supporting devices need not have the form of dat plates but may be otherwise formed.

The main feature of my invention lies in the provision of bracing devices for the main blades 7 and 8, of the propeller and in the structure shown these bracing devices have the form of propelling blades 12 and 13, respectively.

These bracing blades, have a comparatively straight entering edge 1.4L, which, when compared with the direction of rotation of the propeller, has position to the rear of the entering edge 15, of the main blade which it braces, and the trailing edge 16, of each bracing blade projects rearwardly and beyond the trailing edge 17, of the main blade.

The bracing blades have their outer ends secured in bracing relation at the flat side and end of each main blade, a metal clip or other secu-ring device 18, being employed to rigidly secure the two blade-ends in rigid relation. From the outer secured ends the bracing blades incline laterally and at the same time extend slightly to the rear of the main blade so each bracing blade 12 and 13, will form both a lateral brace and a circumferential brace for one main blade.

The inner end 19, of each bracing blade seats against the supporting device or plate 11, and is rigidly attached to the latter by means of fastening devices 20.

From the foregoing explanation it is to be .understood that the bracing blades are located at the advancing side of the main blades so as to brace theI outer thin ends of the blades at that side, and prevent said ends from bending forward as the result of their rearward thrust on the air in driving the craft forward which thrust tends to bend the free ends of the main blades forward and in the direction of flight.

By locating the bracing blades at the advancing side of the main blades with their entering edges 14, at one side but between the entering and trailing edges 15 and 17, respectively of the main blade, the bracing blade during revolution and being forward will operate on an air area different from that operated upon by the main blade and an increased thrust is exerted on the hub and driving shaft over that which the main blades alone would exert.

It is therefore to be understood that the bracing blades not only brace the main blades in both a lateral and a circumferential direction, but said bracing blades increase the thrust of the propeller and materially assist in driving the craft forward.

Having described my invention what l claim` is 1. An air-craft propeller lia-ving a plurality of flat surfaced main blades, and a separate brace for each main blade, each brace havingits outer end connected to the outer end of a main blade and its inner end secured in a trailing position with respect to the inner end of said main blade and in front of the neXt following main blade.

2. An air-craft propeller having a plurality of diametrically opposed main blades,

and a separate brace for each main blade, each brace extending between the hub-end and the outer end of ,a main blade and each brace also extending laterally and rear wardly with respect to the flat side of the main blade it braces and the inner end of each brace having position in front yof the next following main blade.

An air-craft propeller having a plurality of main blades and a bracing blade for each main blade and each bracing blade having its outer end seated against the flat side of and bracing the outer end of a main blade and the inner end of each bracing blade being secured in a spaced and trailing relation with respect to the inner end of said main blade, and means for securing the outer ends of a main and a bracing blade together.

a. An air-craft propeller having a plurality of main blades and vprovided with a separate bracing blade for each main blade, each bracing blade having an entering edge at the forward side of the trailing edge of the main blade it braces and a trailing edge at the rear of the trailing edge of said main blade which it braces.

5. In an air-craft propel-ler the combination with a plurality of main blades, of a separate bracing blade for each main blade,-each bracing blade having a forward entering edge which through a greater portion of its length has position in a plane between the entering and trailing edges of the main blade it braces, means for securing the outer end of each bracing blade to the flat side and outer end of the main blade it braces, and means for securing the inner end of each bracing blade in spaced relation with respect to the hub-end of the main blade it braces.

6. An air-craft propeller having a plurality of straight main blades and an in clined bracing blade for each main blade, each bracing blade having its outer end seated against and secured to the outer end of a main blade and inclining laterally from said outer end toward the inner hub-end, and the inner hub-end of each bracing blade bein@ secured in position at the rear of the trailing edge of the main blade it braces.

7. In an air-craft propeller, the combination with a plurality of straight main blades each having an enteringl edge, a vtrailing edge and an outer end, of a separate bracing blade for each main blade and each bracing blade having a flat surface with an entering edge, and a trailing edge' ywhich edges are located at opposite sides of the trailing edge of the main blade it braces,-the outer end of a bracing blade being secured at the side of the main blade it braces and the inner end of the same bracing blade projecting rearwardly and beyond the trailing edge of the main blade it braces, and being secured at a spaced distance Yfrom the hub-end of the main blade whereby to form an inclined brace for tbe straight main blade.

S. Ain air-craft propeller having a plurality or" main blades and each main blade blade it braces and the inner end of each 10 shorter bracing blade extending rearwardly of the main blade it braces.

In testimony whereof I aHX my signature in the presence of two Witnesses.

RICHARD M. SHAFFER. Witnesses z IZELLA E. BAGLEY, LOUIS C. KLERLEIN. 

